Hospitalisation with otitis media in early childhood and cognitive function in young adult life: A prevalence study among Danish conscripts

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DOI: 10.1186/1471-2431-13-8 · Source: PubMed
Abstract
Background Otitis media (OM) is a very common condition in children and occurs during years that are critical to the development of learning, literacy, and math skills. Therefore, among a large cohort of Danish conscripts, we aimed to examine the association between hospitalisation with OM in early childhood and cognitive function and educational level in early adulthood. Methods We conducted a population-based prevalence study using linked data from healthcare databases and conscription records of Danish men born between 1977 and 1983. We identified all hospitalisations with OM before 8 years of age. Cognitive function was measured by the Boerge Prien validated group intelligence test (Danish Børge Prien Prøve, BPP). We adjusted for potential confounders with and without stratification by hearing impairment. Furthermore, we examined the association between hospitalisation with OM and the prevalence of having achieved a General Certificate of Secondary Education (GCSE), stratified by quartiles of BPP scores. Results Of the 18 412 eligible conscripts aged 18–25 years, 1000 (5.5%) had been hospitalised with OM before age 8. Compared with conscripts without such a record, the adjusted prevalence ratio (PR) for a BPP score in the bottom quartile was 1.20 (95% confidence interval [CI]: 1.09–1.33). There was no major difference in the proportion of men with a GCSE and those without among those hospitalised with OM in early childhood. For men in the bottom and upper quartiles of BPP scores, the PRs for early childhood hospitalisation with OM were 0.89 (95% CI: 0.59–1.33) and 0.96 (95% CI, 0.88–1.05), respectively. Among men with severe hearing impairment, the proportion with a BPP score in the bottom quartile did not differ between those with and without an OM hospitalisation [PR = 1.01 (95% CI: 0.78–1.34)]. Conclusions Overall, we found that hospitalisation with OM in early childhood was associated with a slightly lower cognitive function in early adulthood. Hospitalisation for OM did not seem to influence the prevalence of GSCE when level of BPP was taken into account.

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RES E AR C H A R T I C L E Open Access
Hospitalisation with otitis media in early childhood
and cognitive function in young adult life:
a prevalence study among Danish conscripts
Marie Mortensen
1*
, Rikke Beck Nielsen
1
, Niels Fisker
2
and Mette Nørgaard
1
Abstract
Background: Otitis media (OM) is a very common condition in children and occurs during years that are critical to
the development of learning, literacy, and math skills. Therefore, among a large cohort of Danish conscripts, we
aimed to examine the association between hospitalisation with OM in early childhood and cognitive function and
educational level in early adulthood.
Methods: We conducted a population-based prevalence study using linked data from healthcare databases and
conscription records of Danish men born between 1977 and 1983. We identified all hospitalisations with OM before
8 years of age. Cognitive function was measured by the Boerge Prien validated group intelligence test (Danish
Børge Prien Prøve, BPP). We adjusted for potential confounders with and without stratification by hearing
impairment. Furthermore, we examined the association between hospitalisation with OM and the prevalence of
having achieved a General Certificate of Secondary Education (GCSE), stratified by quartiles of BPP scores.
Results: Of the 18 412 eligible conscripts aged 1825 years, 1000 (5.5%) had been hospitalised with OM before age
8. Compared with conscripts without such a record, the adjusted prevalence ratio (PR) for a BPP score in the
bottom quartile was 1.20 (95% confidence interval [CI]: 1.091.33). There was no major difference in the proportion
of men with a GCSE and those without among those hospitalised with OM in early childhood. For men in the
bottom and upper quartiles of BPP scores, the PRs for early childhood hospitalisation with OM were 0.89 (95% CI:
0.591.33) and 0.96 (95% CI, 0.881.05), respectively. Among men with severe hearing impairment, the proportion
with a BPP score in the bottom quartile did not differ between those with and without an OM hospitalisation
[PR = 1.01 (95% CI: 0.78 1.34)].
Conclusions: Overall, we found that hospitalisation with OM in early childhood was associated with a slightly
lower cognitive function in early adulthood. Hospitalisation for OM did not seem to influence the prevalence of
GSCE when level of BPP was taken into account.
Keywords: Otitis media, Cognitive function, Educational level, Hearing impairment
Background
Acute otitis media (OM) is the most common infectious
disease in young children, having occurred in 80% of all
children by age 3 [1]. Furthermore, acute OM and OM
with effusion (OME) are among the main reasons for
early childhood consultations with general practitioners,
and acute OM is one of the most common reasons for
prescribing antibiotic treatment [2,3].
Since OM occurs in the critical years of language, lit-
eracy, and math skill development [4], OM in early
childhood may affect cognitive function later in life. In a
literature review of Monasta et al., permanent hearing
impairment was found to be a possible effect of OM in
developing countries [5]. In a longitudinal cohort study
of 74 children with early OM, Gravel et al. also found
that mild conductive hearing impairment may influence
auditory abilities in the longe r term but only at high-
* Correspondence: mm@dce.au.dk
Equal contributors
1
Department of Clinical Epidemiology, Aarhus University Hospital, Olof
Palmes Allé 43-45, 8200, Aarhus N, Denmark
Full list of author information is available at the end of the article
© 2013 Mortensen et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the
Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Mortensen et al. BMC Pediatrics 2013, 13:8
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frequency thresholds [6]. Moreover, in a prospective co-
hort study of 73 children with congenital deafness,
Coletti et al. demonstrated improved auditory, speech
language, and cognitive performances in children who
received a cochlear implant prior to 12 months of age
compared with children implanted later [7]. Children
with mild to moderate permanent hearing loss are at risk
for later effects on language and academic developm ent
[8]. In a meta-analysis Roberts et al. found no to very
small effect of OM to speech and language development
in most children [9]. These finding s imply an association
between hearing impairment and cognitive function.
However, the long-term conseque nces of OM are in-
adequately understood, and data on the association be-
tween OM in early childhood and cognitive function in
adulthood are sparse and contradictory. For instance,
Bennett et al. followed a birth cohort of 1000 children
into their teens and found that a history of ea rly middle
ear disease appeared to affect reading ability, verbal
intelligence quotient, and behavior problems [10]. In
contrast, Zumach et al. found in a cohort study of 65
children that OM in early childhood was associated with
hearing impairment, which de creased language compre-
hension and language skills at age 2, but not at age 7
[11]. Similarly, Grievink et al. found no correlation be-
tween the effects of OME and linguistic ability at age 7
in a cohort of 305 children [12]. In addition, the pro-
spective study of 698 children by Johnson et al. found
that prolonged OME wa s associated with decreased cog-
nitive function at age 3, but that this association was not
found by ages 57 [13]. Finally, in a prospective study of
241 children at 3 years of age, Paradise et al. found no
correlation between the duration of OME and verbal
aspects of cognition [14].
As cognitive function ha s been examined predomin-
antly in early childhood and with school-age children,
whether or not OM in early childhood and it s possible
impact on cognitive function also affects the level of
education achieved is also not fully clarified [10-14].
Along these lines, a previous study by Welch and Dawes
found no association between early childhood middle
ear disease and adult measures of education [15].
Therefore, we examined the association between hos-
pitalisation with OM in early childhood and cognitive
function and educational level in young adult life using a
large Danish army conscript data registry.
Methods
We conducted a prevalence study based on registry
data collected in the Fifth Military Conscription District
of Denmark, which includes the former counties of
North Jutland and Viborg (population approximately
700 000). We included all men born as singletons from
January 1, 1977, to December 31, 1983, who registered
in the Fifth Military Conscription District from 1997 to
2003. Evaluation at the military draft board is mandatory
for all Danish men aged 1820 years. Men must register
with authorities in one of the countrys conscription dis-
tricts, which were determined by their place of residence
at age 18. During registration, men can report conditions
that potentially preclude military service. Draft board
physicians verify these reports and men with a verified
condition are exempted from military duty without fur-
ther examination. Documentation for the diagnosis lead-
ing to exemption is filed in the Conscript Registry and
coded according to the 10th revision of the International
Classification of Diseases (ICD-10) [16].
Otitis media
We used the civil registration number (a unique personal
identifier assigned at birth) to link data from the Conscript
Registry to information on previous hospitalisations for
OM recorded in the Danish National Registry of Patients
(DNRP) [17]. The DNRP contains data on all hospitalisa-
tions in Denmark since 1977, including civil registration
numbers and diagnoses coded according to the Inter-
national Classification of Diseases eighth revision (ICD-8)
until 1994, and the tenth revision thereafter [16].
We defined hospitalisation with OM as at least one hos-
pital diagnosis of OM (ICD-8 codes 381 and 382) regis-
tered before the age of 8, since the prevalence of OM
among Danish children is highest in this age group [18].
Thus, we included cases of OM with and without mastoid-
itis, acute OM, OME, and chronic suppurative OM. Here-
after, OM refers to any of these different types of OM.
Cognitive function and educational level
All men who attend the evaluation at their military draft
board must take a 45-minute group intelligence test, the
Boerge Prien test (Danish Børge Prien Prøve, BPP), which
has been used since 1957 by Danish military draft boards
[19]. The test includes four time-limited subtests: letter
matrices, verbal analogies, number series, and geometric
figures. The single final score is the sum of correctly
answered items (range: 078). BPP scores correlate to a
large extent with scores in the Wechsler Adult Intelligence
Scale (WAIS) (correlation coefficient = 0.82), although the
BPP is a group test and the WAIS is an individually-
administered test. Nevertheless, both tests are assumed to
measure general intelligence [19]. From the conscript
records, we also obtained information on whether the
conscripts had achieved or were currently achieving the
General Certificate of Secondary Education (GCSE), which
is typically achieved at the age of 18 or 19 in Denmark.
Covariates
We obtained information on gestational factors from the
Danish Medical Birth Registry, which has tracked all
Mortensen et al. BMC Pediatrics 2013, 13:8 Page 2 of 8
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births in Denmark since January 1, 1973 [20]. The infor-
mation is derived from birth notification forms com-
pleted by midwives attending the birth. Variables include
civil registration number, date and place of birth, gesta-
tional age, birth weight, maternal parity, and, since 1978,
information on maternal marital status and Apgar score.
Given that permanent hearing impairment may be a
consequence of OM in developing countries [5] and
hearing impairment is also associated with cognitive
function [7,8], we obtained information on hearing from
conscript records. At the conscript examination an
audiometric test is performed. The recording of the
audiogram mea surements are undertaken at frequencies
500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz. Initial
screening are carried out equivalent to 20 decibel [21].
Hearing is classified on a scale from 05 (severe hearing
impairment to no hearing impairment). To improve the
precision of the estimates, we collapsed the scale into se-
vere hearing impairment (03), moderate hearing im-
pairment (4), and no hearing impairment (5).
Statistical analysis
We first constructed a box-and-whisker plot of BPP
score distributions according to age at first hospitalisa-
tion for OM. We defined low cognitive function as a
BPP score in the bottom quartile and used a log-
binomial regression to estimate crude and adjusted
prevalence ratios (PRs) for a BPP score in this quartile,
according to age at first hospitalisation for OM [22]. PRs
for a BPP score in the bottom quartile were estimated
and stratified according to hearing impairment measured
at the time of conscription examination.
The following possible confounding factors were
included as identified from the literature: birth order (0, 1,
2, 3+), maternal age (20, 2135, >35 years), marital status
(married/unmarried), 5-minute Apgar score (<7, 710),
gestational age, a composite variable derived from gesta-
tional age and birth weight [small for gestational age
(SGA) or not] [23], and hea ring score at conscription
(severe, moderate, or no hearing impairment). In the
regression analysis all variables were entered as sets of
indicator variables. In a separate analysis we additionally
adjusted for a previous diagnosis of febrile seizures or epi-
lepsy. We examined PRs for OM hospitalisation and GCSE
stratified into four quartiles by BPP score. To avoid loss of
observations, missing values were estimated using multiple
imputations, such that five imputed datasets were created
and analysed with their averages serving as the estimates
[24,25]. The regression model used for imputation
included variables for gestational age, SGA or non-SGA,
birth order, maternal age, marital status, and Apgar score
5-minutes after birth [26]. Confidence intervals (CI)
around these estimates reflect uncertainty both about the
value of the PRs and about the imputed values.
There was a lack of cognitive data on the exempted men
because many of the conscripts (11.9%) were exempted
from draft board examination. To quantify this potential
selection bias, a sensitivity analysis was performed in which
the regression analyses were repeated with imputation of
BPP scores for all the 2470 exempted men. To assess the
maximal impact of a potential selection bias, the regression
analyses for the worst case scenario and best case scenario
was repeated assuming that all exempt men had a BPP
score in the bottom quartile and no exempt men had a
BPP in the bottom quartile, respectively. Model-estimated
PRs were compared with corresponding pooled Mantel-
Haenszel (non-parametric ) estimates. In an additional ana-
lysis, all men with a previous diagnosis of meningitis were
excluded (68 men out of 18 412 in the study population).
Data were analysed using Stata software, version 11.2
(Stata, 4905 Texas, USA).
The study was approved by the Danish Data Protec-
tion Agency (http://www.datatilsynet.dk/english/, record
no. 2011-41-5807). Data were obtained from the Con-
script Registry, Danish Medical Birth Regist ry, and the
DNRP. According to Danish legislation the study did not
require permission from a Scientific Ethical Committee.
Results
Descriptive data
A total of 21 051 men born as singletons during the
19781983 period were registered in the Fifth Conscrip-
tion District of Denmark. Of these, 161 (0.8%) had been
hospitalised with OM after the age of 8. Of the eligible
men, 2470 (11.7%) were exempt from draft board evalu-
ation for health reasons. BPP scores were missing for 8
of the 18 420 non-exempt men (0.04%), leaving 18 412
men in the analysis (descriptive data are presented in
Table 1). Of these, 1000 men (5.4%) had been hospita-
lised with OM before age 8.
The prevalence of exemption prior to draft board
evaluation was 20% for men hospitalised with OM in
early childhood and 11% for men with no record of a
hospitalisation with OM.
For the non-exempt conscripts, the median BPP scores
were 42 (interquartile range: 3548) for men with an
OM hospitalisation and 44 (interquartile range: 3850)
for men without an OM hospitalisation (Table 1). Most
cases of hospitalisation with OM (37%) occurred in the
second year of life. The median BPP scores varied be-
tween 41 and 44 (see Figure 1) when stratified according
to age at first hospitalisation with OM.
Prevalence ratios for Boerge Prien test (BPP) scores
The prevalences of BPP scores in the bottom quartile
(score 37) were 31.2% (312/1000) for men hospitalised
with OM in early childhood and 25.1% (4370/17 412) for
men without such a hospitalisation.
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Among men without hearing impairment at the time
of draft board evaluation, those who had been hospita-
lised with OM in early childhood had a 15% greater risk
of a BPP score in the bottom quartile than the other men
in the study (Table 2). Among men with severe hearin g
impairment (7.9% of men with OM hospitalisation and
4.4% of the men without), the proportions with a BPP
score in the bottom quartile were similar [PR = 1.01 (95%
CI: 0.781.34)].
Compared with men without childhood hospitalisation
for OM, the adjusted PR for a BPP score in the bottom
quartile for men with an OM hospitalisation was 1.20
Table 1 Characteristics of conscripts, who were evaluated at the draft board and had a Boerge Prien test (BPP)
Otitis media hospitalisation in childhood
Variables Yes No Total
Men evaluated by the draft board, n (%) 1000 (5.4%) 17 412 (94.6%) 18 412 (100%)
BPP score, median (interquartile range) 42 (3548) 44 (3850) 44 (3850)
Proportion with a BPP score in the bottom quartile (%) 312 (31.2%) 4370 (25.1%) 4682 (25.4%)
Birth weight in grams, median (interquartile range) 3450 (31253760) 3510 (31603875) 3500 (31503875)
Gestational age, no. (%)
Preterm (<37 weeks) 53 (5.3%) 648 (3.7%) 701 (3.8%)
Term (3141 weeks) 708 (70.8%) 12 762 (73.3%) 13 470 (73.2%)
Post-term (42 weeks) 66 (6.6%) 1209 (6.9%) 1275 (6.9%)
Missing 2793 (16.0%) 173 (17.3%) 2966 (16.1%)
Small for gestational age, no. (%)
Yes 17 (1.7%) 141 (0.8%) 158 (0.9%)
No 808 (80.8%) 14 385 (82.6%) 15 193 (82.5%)
Missing 175 (17.5%) 2886 (16.6%) 3061 (16.6%)
Apgar score at 5 minutes after birth, no. (%)
<7 6 (0.6%) 99 (0.6%) 105 (0.6%)
7 908 (90.8%) 16 077 (92.3%) 16 985 (92.2%)
Missing 86 (8.6%) 1236 (7.1%) 1322 (7.2%)
Maternal age, n (%)
20 years 100 (10.0%) 1638 (9.4%) 1738 (9.4%)
2135 years 852 (85.2%) 14 794 (84.9%) 15 646 (84.9%)
> 35 years 48 (4.8%) 980 (5.6%) 1028 (5.6%)
Mothers marital status at subjects birth, n (%)
Married 595 (59.5%) 11 033 (63.4%) 11 628 (63.2%)
Unmarried 341 (34.1%) 5366 (30.8%) 5707 (31%)
Missing 64 (6.4%) 1013 (5.8%) 1077 (5.9%)
Birth order, n (%)
1 320 (32.0%) 6063 (34.8%) 6383 (34.7%)
2 368 (36.8%) 6148 (35.3%) 6516 (35.4%)
3 183 (18.3%) 3173 (18.2%) 3356 (18.2%)
4+ 129 (12.9%) 2026 (11.6%) 2155 (11.7%)
Missing 0 (0%) 2 (0.01%) 2 (0.01%)
Mode of delivery, no. (%)
Vaginal 796 (79.6%) 14 170 (81.4%) 14 966 (81.3%)
Caesarean 119 (11.9%) 1626 (9.3%) 1745 (9.5%)
Forceps or vacuum extraction 85 (8.5%) 1616 (9.3%) 1701 (9.2%)
Hearing score at conscription, no. (%)
Severe hearing impairment 78 (7.8%) 754 (4.3%) 832 (4.5%)
Moderate hearing impairment 274 (27.4) 3902 (22.4%) 4176 (22.7%)
No hearing impairment 641 (64.1%) 12 653 (72.7%) 13 294 (72.2%)
Missing 7 (0.7%) 103 (0.6%) 110 (0.6%)
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(95% CI: 1.091.33) (Table 3). None of the potential con-
founding variables noticeably affected the PR estimates,
either separately or in combination. Including men who
did not come to the conscription examination by imput-
ing their BPP values did not changes the estimates.
There was no major variation in the prevalence of
GCSE by quartiles of BPP scores amon g men with and
without an OM hospit alisation in early childhood, as the
PR was 0.89 (95% CI: 0.591.33) for those in the bottom
quartile of BPP scores and 0.96 (95% CI: 0.881.05) for
those in the upper quartile (Table 4). Excluding men
who previously had been diagnosed with meningitis also
did not change the estimates.
Assuming the worst case scenario, with all exempt
men having a BPP score in the bottom quartile, resulted
in a PR of 1.29 (95% CI, 1.21 to 1.38), while the surplus
for the best case scenario was a PR of 1.09 (95% CI, 0.99
to 1.21).
Discussion
In this study of 18 412 conscripts, we examined long-
term cognitive outcomes after hospitalisation for OM
before age 8. Overall, we found that hospitalisation with
OM in early childhood was associated with a slightly
lower cogni tive function in early adulthood except in
0 20 40 60 80
Boerge Prien test score
<1(N=83) 1(N=371) 2(N=157) <3(N=92) 4(N=110) 5(N=77) 6(N=66) 7(N=44) Ref(N=17412)
A
g
e at hospital dischar
g
e with first otitis media in full years
Figure 1 BPP scores by age at first hospitalisation diagnosis with otitis media (OM) in Danish conscripts. The group comprised conscripts
without a hospitalisation with OM. The cross marks the median of a BPP score, and the box marks the upper and lower quartiles. The whiskers
extend 1.5 times the interquartile range. Observations outside that range are plotted individually. The horizontal line shows sample median BPP,
which equals 44.0.
Table 2 Distribution of Boerge Prien test (BPP) scores and
prevalence ratios, stratified according to hearing score
Otitis media hospitalisation
in childhood
Yes No
Severe hearing impairment
(hearing score 03)
Number, % 78 (7.9%) 754 (4.4%)
Median BPP (quartile) 40 (3247) 39 (3346)
Men with a BPP in the bottom quartile 33 (42.3%) 313 (41.5%)
PR for BPP in the bottom quartile, 95% CI 1.01 (0.781.34) 1 (reference)
Moderate hearing impairment
(hearing score 4)
Number, % 274 (27.6%) 3902 (22.5%)
Median BPP (quartile) 41 (3346) 43 (3849)
Men with a BPP in the bottom quartile 105 (38.3%) 1107 (28.4%)
PR for BPP in the bottom quartile, 95% CI 1.35 (1.151.58) 1 (reference)
No hearing impairment
(hearing score 5)
Number, % 641 (64.6%) 12 653 (73.1%)
Median BPP (quartile) 43 (3849) 44 (3850)
Men with a BPP in the bottom quartile 169 (26.4%) 2908 (22.9%)
PR for BPP in the bottom quartile, 95% CI 1.15 (1.011.32) 1 (reference)
Total 993 (100%) 17 309 (100%)
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men with severe hearing impairment at the time of draft
board evaluation. We found no association between hos-
pitalisation for OM in early childhood and GCSE beyond
that explained by level of cognitive function.
Our stud y thus extends the findings by Bennett et al.
who found that some developmental sequelae of OME
could continue into the early teens [10]. Our findings
are in contrast to the studies of Roberts et al., Zumach
et al., Grievink et al., and Johnson et al. [9,11-13] who
could not detect any ne gative consequences of OM and
OME by 7 years of age. However, these studies were all
smaller than our population-based study. Additionally,
our findings also agree with those of Welch and Dawes,
which indicate that OM in early childhood does not
affect the level of education attained [15].
We only focused on those admitted to the hospit al for
OM in early childhood. By age 3 it is estimated that 80%
of all children have experienced at least one episode of
OM [1], though only a minority of these children are ad-
mitted to the hospital. Admitted cases presumably repre-
sent more severe cases of OM. Still, other factors may
influence whether or not a child is admitted to the hos-
pital for OM, such as socioeconomic status (SES). Un-
fortunately, we had limited information on SES and
were thus unable to determine whether our observed as-
sociation could be explained by severity of OM or by
other factors influencing hospitalisation for OM. In
addition, hearing impairment is probably also related to
the severity of OM [5]. Yet, when we stratified according
to hearing impairment at conscription examination, we
found no differences in BPP among men hospitalised for
OM in early childhood. This could indicate that the cor-
relation between OM and low BPP cannot be explained
by hearing loss alone.
Our study has other strengths and limitations. The
possibility of certain types of selection biases was
reduced by independent collection of data on OM and
BPP scores in a population with tax-funded free access to
health care and free hospitalisations, if indicated. Still, we
examined outcomes among men who survived and
stayed in the region to conscription age, rather than fol-
lowing a birth cohort. We also lacked data on the cogni-
tive function of men exempt from conscript examination;
if some were exempt because of conditions related to
OM and lower cognitive function, we may have underes-
timated the association between hospitalisation for OM
and cognitive function in young adulthood [19]. How-
ever, imputing BPP scores for exempt men did not
change our results. The sensitivity analysis showed that
the risk of significant selection bias, because of the ex-
empt men was minimal. In addition, our study relied on
hospitalisation diagnoses, which may not have been
Table 3 Crude and adjusted prevalence ratios for Boerge Prien test (BPP) scores overall and according to age
Total men with BPP score in the bottom quartile PR for BPP score in the bottom quartile
n (%) n (%)
Crude PR Adjusted* PR
Hospitalisation with OM
No 17 412 4370 (25.1) 1 1
Yes 1000 312 (31.2) 1.24 (1.131.37) 1.20 (1.091.33)
Age at first hospitalisation with OM
< 1 year 83 30 (36.1) 1.44 (1.081.92) 1.38 (1.041.83)
12 years 528 163 (31.0) 1.23 (1.071.40) 1.17 (1.031.33)
35 years 279 85 (30.5) 1.22 (1.021.45) 1.24 (1.031.49)
67 years 110 34 (30.9) 1.23 (0.931.63) 1.17 (0.891.54)
*Based on log binomial regression using multiple imputation for the following variables: gestational age (<37, 3741, >41), gestational age adjusted birth weight
(SGA, non-SGA), birth order (1,2,3,4+), maternal age (20, 2135, >35 yea rs), marital status (married/unmarried), and Apgar score 5-minutes after birth (<7, 7).
Table 4 Prevalence of GCSE among conscripts with and without hospitalisation for otitis media (OM), stratified by
Boerge Prien test (BPP) scores
With GCSE Without GCSE
With OM n,% Without OM n,% With OM n,% Without OM n,% PR
BPP 37 23 (7.4) 363 (8.3) 288 (92.6) 4000 (91.7) 0.89 (0.591.33)
BPP 3844 89 (28.7) 1481 (31.2) 221 (71.3) 3272 (68.8) 0.92 (0.771.10)
BPP 4550 104 (52.8) 2389 (55) 93 (47.2) 1954 (45) 0.96 (0.841.10)
BPP >50 134 (74.0) 3022 (76.9) 47 (26) 906 (23.1) 0.96 (0.881.05)
Total 7605 (41.4) 10 781 (58.6)
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accurately registered [27]. Misclassification of the OM
diagnosis could have biased our relative estimates toward
the null. Moreover, we were able to control for several ges-
tational factors, but we lacked information on variables
related to maternal lifestyle, such as smoking, alcohol in-
take, and medication use. We also lacked information on
the home environment, day-care attendance, and further
social factors of the conscripts as children, all of which
may be potential confounding factors [10,28-31]. Although
adjustment for measured confounders led to only minor
changes in our estimates, unmeasured confounding can
not be excluded as a potential explanation for the associa-
tions found in this study.
Conclusion
Overall, we found a slightly lower cogn itive function in
early adulthood among men who were hospitalised with
OM in early childhood. Further, we found no association
between hospitalisation with OM and GCSE when the
level of BPP wa s taken into account.
Endnote
a
General Certificate of Secondary Education: is refer-
ring to the Danish Upper Secondary School Leaving
Examination.
Abbreviations
BPP: Boerge Prien test (Danish Børge Prien Prøve); DNRP: Danish National
Registry of Patients; GCSE: General Certificate of Secondary Education
a
;
ICD: International Classification of Diseases; PR: Prevalence ratio; OM: Otitis
media; OME: Otitis media with effusion; SES: Socioeconomic status;
WAIS: Wechsler Adult Intelligence Scale.
Competing interests
The authors declare that they have no competing interests and no financial
relations to disclose that are relevant to this article.
Authors contributions
MM, RBN, NF, and MN contributed to the conception and design of the
study. MM, RBN, and MN contributed to the analysis of the data. All authors
contributed to the interpretation of the data, drafting or revising of the
manuscript, and final approva l for publication. MM and MN are the
guarantors.
Acknowledgements
The study received financial support from the Clinical Epidemiological
Research Foundation.
Author details
1
Department of Clinical Epidemiology, Aarhus University Hospital, Olof
Palmes Allé 43-45, 8200, Aarhus N, Denmark.
2
H.C. Andersen Childrens
Hospital, Odense University Hospital, Sdr. Boulevard 29, 5000, Odense C,
Denmark.
Received: 6 July 2012 Accepted: 11 January 2013
Published: 15 January 2013
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Cite this article as: Mortensen et al.: Hospitalisation with otitis media in
early childhood and cognitive function in young adult life: a prevalence
study among Danish conscripts. BMC Pediatrics 2013 13:8.
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  • [Show abstract] [Hide abstract] ABSTRACT: Objective: To examine the association between hospitalisations for otitis media and area-level measures of household crowding among children in New Zealand.Methods: Counts of hospital admissions for otitis media by census area unit were offset against population data from the 2006 national census. Area-level household crowding, exposure to tobacco smoke in the home, equivalised income and individual-level characteristics age and sex were adjusted for. To examine effect modification by ethnicity, three separate poisson models were examined for the total, Māori and non-Māori populations.Results: Household crowding was significantly associated with hospital admissions for otitis media after adjustment in all three models. Neighbourhoods with the highest compared to the lowest proportion of crowded homes exhibited incidence rate ratios of 1.25 (95%CI 1.12–1.37) in the total population, 1.59 (95%CI 1.21–2.04) in the Māori restricted model and 1.17 (95%CI 1.06–1.32) in the non-Māori restricted model.Conclusions: Otitis media hospitalisations are associated with area-level measures of household crowding and other risk factors in this ecological study. The largest increase in otitis media incidence relative to neighbourhood rates of household crowding was exhibited among Māori cases of otitis media.Implications: This study adds weight to the growing body of literature linking infectious disease risk to overcrowding in the home.
    Full-text · Article · Apr 2014